Beede.] Carboniferous Invertebrates. 131 



Limopteria subalata. Plate XXI, figs. 3a, 3b. 



Monopteriat subalata Beede and Rogers, Kans. Univ. Quart., vnr, p. 

 133, pi. xxxiv, tf. 3a, 3b, (1899). 



Shell moderate!}- small, subcrescentic in outline, gibbous, a 

 little longer than high ; valves sulbequal, but beak prominent, 

 slightly projecting, somewhat inflated, situated about one-fifth 

 the length of the shell from the anterior margin, which is trun- 

 cated, on account of the lunule which is formed by the turning 

 in of the shell. The anterior margin is convex below. Ventral 

 margin broadly rounded to the postero- ventral extremity, where 

 it is abruptly rounded to meet the concave posterior. Hinge 

 short and straight ; posterior ear but slightly developed ; utn- 

 bonal ridge prominent, somewhat sickle-shaped, sloping abruptly 

 posteriorly, forming a cavity broadly convex anteriorly. Sur- 

 face marked by moderately distinct lines of growth. Length, 

 l'i mm. ; height, 14 mm. ; convexity of single valve, 4 mm. 



Range and distribution: Upper Coal Measures; Lawrence, 

 Topeka. 



At two localities in the lower part of the Upper Coal Meas- 

 ures are found great numbers of Limopteria. Beside the three 

 large species are found two smaller species, L. alata and L. sub- 

 alata ; one with an exceedingly large wing and compressed shell, 

 and the other with a gibbous shell and the wing almost want- 

 ing. There are many variations of the two species and they 

 seem to grade into the other species to some extent, but differ 

 sufficiently, so far as we can observe, from even the young of 

 those, to be considered as distinct. 



The size of the shell and the exceedingly small ear easily 

 separate L. subalata from any other member of the genus. 



